# - Returns a version string from Git
#
# These functions force a re-configure on each git commit so that you can
# trust the values of the variables in your build system.
#
#  get_git_head_revision(<refspecvar> <hashvar> [<additional arguments to git describe> ...])
#
# Returns the refspec and sha hash of the current head revision
#
#  git_describe(<var> [<additional arguments to git describe> ...])
#
# Returns the results of git describe on the source tree, and adjusting
# the output so that it tests false if an error occurs.
#
#  git_get_exact_tag(<var> [<additional arguments to git describe> ...])
#
# Returns the results of git describe --exact-match on the source tree,
# and adjusting the output so that it tests false if there was no exact
# matching tag.
#
# Requires CMake 2.6 or newer (uses the 'function' command)
#
# Original Author:
# 2009-2010 Ryan Pavlik <rpavlik@iastate.edu> <abiryan@ryand.net>
# http://academic.cleardefinition.com
# Iowa State University HCI Graduate Program/VRAC
#
# Copyright Iowa State University 2009-2010.
# Distributed under the Boost Software License, Version 1.0.
# (See accompanying file LICENSE_1_0.txt or copy at
# http://www.boost.org/LICENSE_1_0.txt)

if(__get_git_revision_description)
        return()
endif()
set(__get_git_revision_description YES)

# We must run the following at "include" time, not at function call time,
# to find the path to this module rather than the path to a calling list file
get_filename_component(_gitdescmoddir ${CMAKE_CURRENT_LIST_FILE} PATH)

function(get_git_head_revision _refspecvar _hashvar)
        set(GIT_PARENT_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
        set(GIT_DIR "${GIT_PARENT_DIR}/.git")
        while(NOT EXISTS "${GIT_DIR}")	# .git dir not found, search parent directories
                set(GIT_PREVIOUS_PARENT "${GIT_PARENT_DIR}")
                get_filename_component(GIT_PARENT_DIR ${GIT_PARENT_DIR} PATH)
                if(GIT_PARENT_DIR STREQUAL GIT_PREVIOUS_PARENT)
                        # We have reached the root directory, we are not in git
                        set(${_refspecvar} "GITDIR-NOTFOUND" PARENT_SCOPE)
                        set(${_hashvar} "GITDIR-NOTFOUND" PARENT_SCOPE)
                        return()
                endif()
                set(GIT_DIR "${GIT_PARENT_DIR}/.git")
        endwhile()
        # check if this is a submodule
        if(NOT IS_DIRECTORY ${GIT_DIR})
                file(READ ${GIT_DIR} submodule)
                string(REGEX REPLACE "gitdir: (.*)\n$" "\\1" GIT_DIR_RELATIVE ${submodule})
                get_filename_component(SUBMODULE_DIR ${GIT_DIR} PATH)
                get_filename_component(GIT_DIR ${SUBMODULE_DIR}/${GIT_DIR_RELATIVE} ABSOLUTE)
        endif()
        set(GIT_DATA "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/git-data")
        if(NOT EXISTS "${GIT_DATA}")
                file(MAKE_DIRECTORY "${GIT_DATA}")
        endif()

        if(NOT EXISTS "${GIT_DIR}/HEAD")
                return()
        endif()
        set(HEAD_FILE "${GIT_DATA}/HEAD")
        configure_file("${GIT_DIR}/HEAD" "${HEAD_FILE}" COPYONLY)

        configure_file("${_gitdescmoddir}/get_git_revision_description.cmake.in"
                "${GIT_DATA}/grabRef.cmake"
                @ONLY)
        include("${GIT_DATA}/grabRef.cmake")

        set(${_refspecvar} "${HEAD_REF}" PARENT_SCOPE)
        set(${_hashvar} "${HEAD_HASH}" PARENT_SCOPE)
endfunction()

function(git_describe _var)
        if(NOT GIT_FOUND)
                find_package(Git QUIET)
        endif()
        get_git_head_revision(refspec hash)
        if(NOT GIT_FOUND)
                set(${_var} "GIT-NOTFOUND" PARENT_SCOPE)
                return()
        endif()
        if(NOT hash)
                set(${_var} "HEAD-HASH-NOTFOUND" PARENT_SCOPE)
                return()
        endif()

        # TODO sanitize
        #if((${ARGN}" MATCHES "&&") OR
        #	(ARGN MATCHES "||") OR
        #	(ARGN MATCHES "\\;"))
        #	message("Please report the following error to the project!")
        #	message(FATAL_ERROR "Looks like someone's doing something nefarious with git_describe! Passed arguments ${ARGN}")
        #endif()

        #message(STATUS "Arguments to execute_process: ${ARGN}")

        execute_process(COMMAND
                "${GIT_EXECUTABLE}"
                describe
                ${hash}
                ${ARGN}
                WORKING_DIRECTORY
                "${CMAKE_CURRENT_SOURCE_DIR}"
                RESULT_VARIABLE
                res
                OUTPUT_VARIABLE
                out
                ERROR_QUIET
                OUTPUT_STRIP_TRAILING_WHITESPACE)
        if(NOT res EQUAL 0)
                set(out "${out}-${res}-NOTFOUND")
        endif()

        set(${_var} "${out}" PARENT_SCOPE)
endfunction()

function(git_get_exact_tag _var)
        git_describe(out --exact-match ${ARGN})
        set(${_var} "${out}" PARENT_SCOPE)
endfunction()
